Sensor-fuzed munitions are a class of air-to-ground “smart weapons” that use the body dynamics of a projectile, or “munition”, to continuously translate the instantaneous sensor field of view to thoroughly search the suspected target area. A munition is placed in motion over a region of interest. Such motion may be induced in a number of different ways, for example, by ejecting the munition from a propulsion vehicle such as a missile, by dropping the munition from an aircraft, or by launching the munition from a ground-based launch system canister such as a wide-area munition (WAM) launch system, for example, of the type disclosed in U.S. Pat. No. 6,820,341, incorporated herein by reference. Other systems and methods for munition extraction are disclosed in U.S. Pat. No. 6,666,145, incorporated herein by reference. The munitions can be dispensed individually, or a plurality of munitions, i.e. “submunitions”, can be scattered from a common delivery vehicle in a cluster pattern to blanket a target area. During flight of each munition, on-board “sensors” scan for targets within the region of interest and, if a target is located, that information is used to “fuze”, or activate, a warhead on the munition when the warhead is aimed at the target; hence the name “sensor-fuzed” munition.
Upon dispensing, the munition is at a given altitude and is caused to spin. As it descends from that altitude, over the region of interest, on-board sensors and corresponding processors are activated and instructed to search along the circumference of a conical scan pattern for “target-like” objects that meet the sensor algorithm criteria. The offset angle of the scan beam of the scanning instruments to the line of flight remains approximately the same during the flight. Revolution of the munition at a constant offset angle about a vertical trajectory axis, combined with the continuous descent of the munition, causes the radius of the search pattern at the intersection of the scan cone and the ground to continuously decrease, such that the scanning operation of the region of interest follows an inward spiral pattern. Deceleration technology and spin-inducing technology can be employed to arrest the ballistic path of the munition. Such technology includes a Samara wing, as disclosed in U.S. Pat. Nos. 4,583,703 and 4,635,553, incorporated herein by reference. Other deceleration and spin-inducing technologies include a parachute systems and hinged-mass systems that include an offset mass that cause the munition to spin at the offset angle about the axis of the direction of fall or simply inducing the dynamics by the action of dispense without any other decelerator or cone inducing mechanism as is done in the USAF Sensor Fuzed Weapon and the US Army Hornet.
On-board sensor systems for conventional sensor-fuzed munitions include a dual-mode infrared sensor and a laser rangefinder. The infrared sensor is a passive sensor that receives infrared energy from the background and target-like objects located in the field of view. The collected infrared data is used to search for targets that algorithmically match defined infrared signature parameters. The laser rangefinder provides a height profile to the target algorithm for improved aim point selection and greater lethality. The laser rangefinder is an active sensor including a laser transmitter that emits a laser pulse for each successive incremental foot of observation in the direction of the scan. A reflection of the transmitted pulse is received at a laser receiver and the time-of-flight of the, as reflected by the ground or the target, is measured. Processors coupled to the sensors analyze received sensor data to determine whether a target is present within the scanned region. A decision is reached by the processors, based on the sensor data and the algorithm applied, whether to trigger a stand-off warhead on the munition, such as an explosively formed penetrator (EFP), to strike the targeted object with a high-speed projectile.
Conventional applications of sensor-fuzed munition technology include the USAF Sensor Fuzed Weapon (SFW), the US Army “Hornet” off-route mine, the US Army Sense And Destroy (SADARM) 155 mm artillery projectile, the German “Smart 155” 155 mm projectile and the Swedish/French “BONUS” 155 mm projectile. While these applications have proven effective in searching for and attacking enemy target vehicles, uncertainty in the application of the detection criteria of the conventional sensor-fuzed munition to military targets and civilian vehicles is still very high. This target uncertainty is undesirable in modern warfare where minimization of collateral damage and decrease in the likelihood of engagement of an other-than-intended target(s) are of utmost concern.